1. Field of the Invention
The invention relates to an inlet device for charging shallow grit chambers with waste water having a feed line into and a drain line out of, a rectangular tank.
The invention also relates to an inlet device for charging settling tanks.
The invention relates, on the one hand, to a method of charging such shallow grit chambers and also to a method of charging such settling tanks.
2. Description of the Prior Art
To separate grit from the waste water, grit chambers are used in a known manner in sewage treatment plants with the objective of obtaining a clean sand, i.e. a sand largely free of organic admixtures, regardless of variations in the waste water inflow. Common to these grit chamber structures of a very wide variety of designs is the fact that they exploit gravity (in the case of a shallow grit chamber) or gravity and centrifugal force (in the case of hydrocyclones and circular tanks) to separate grit from waste water. The advantage of the grit chambers last mentioned compared with those based on the pure gravitational principle, must, however, not be assessed too highly in relation to the sizing effect because of the relatively low radial acceleration. The grit is separated essentially under the influence of gravity. The circular and spiral movement of the waste water effected by the shape of these grit chambers is used primarily to convey solids into the grit collecting chamber.
The technological background to the construction of shallow grit chambers is that the mineral constituents down to a separation size of d.sub.p .gtoreq.0.1 to 0.2 mm are to be separated from the waste water, while the organic components are to be conveyed further to the downstream purification stages. For this purpose, shallow grit chambers are predominantly used. The shallow grit chambers are charged horizontally via a pipeline. In that case, to even out the flow, grids or baffle plates, which, according to Dr. -Ing. H. Patt (Institute for Water Usage, University of the Federal German Army, Munich, 1990, ISSN 0720-1273), do not, however, have any effect on the total retention factor, are often arranged in the inlet region. In the case of the horizontal flow through the shallow grit chamber, the organic particles contained in the waste water are then separated with the aid of gravity by means of the different settling rates. Depending on the amount of inflow, a grit chamber minimum length, which, according to Camp, can be determined by measuring the surface charging, is necessary for the settling process.
On the other hand, it is not denied that, in the case of settling tanks, it is known to feed them from a feed channel via a certain number of inlet pipes. In the case of a settling tank it is important to achieve a uniform and low flow as quickly as possible.